Volcanic cone: Difference between revisions
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A spatter cone is formed of molten lava ejected from a vent somewhat like taffy. Expanding gases in the lava fountains tear the liquid rock into irregular gobs that fall back to earth, forming a heap around the vent. The still partly liquid rock splashes down and over the sides of the developing mound is called ''spatter''. Because spatter is not fully solid when it lands, the individual deposits are very irregular in shape and weld together as they cool, and in this way particularly differ from cinder and ash. Spatter cones are typical of volcanoes with highly fluid magma, such as those found in the [[Hawaiian Islands]]. |
A spatter cone is formed of molten lava ejected from a vent somewhat like taffy. Expanding gases in the lava fountains tear the liquid rock into irregular gobs that fall back to earth, forming a heap around the vent. The still partly liquid rock splashes down and over the sides of the developing mound is called ''spatter''. Because spatter is not fully solid when it lands, the individual deposits are very irregular in shape and weld together as they cool, and in this way particularly differ from cinder and ash. Spatter cones are typical of volcanoes with highly fluid magma, such as those found in the [[Hawaiian Islands]]. |
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==Ash and tuff cones== |
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An ash cone is composed of particles of silt to [[sand]] size. Explosive eruptions from a vent where the [[magma]] is interacting with [[groundwater]] or the [[sea]] (as in an eruption off the coast) produce steam and are called ''phreatic''. The interaction between the magma, expanding steam, and volcanic gases results in the ejection of mostly small particles called ''[[volcanic ash| ash]]''. Fallen ash has the consistency of [[flour]]. The unconsolidated ash forms an ''ash cone'' which becomes a ''tuff cone'' or ''[[tuff ring]]'' once the ash consolidates (see also [[tuff]]). The term ''pyroclastic cone'' is often used synonymously with ''tuff cone.'' |
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An example of a tuff cone is [[Diamond Head, Hawaii|Diamond Head]] at [[Waikiki|Waikīkī]] in [[Hawaii|Hawai{{okina}}i]]. |
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See also: [[List of pyroclastic cones]] |
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==Cinder cone== |
==Cinder cone== |
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Revision as of 13:57, 6 March 2009
Volcanic cones are among the simplest volcano formations in the world. They are built by fragments (called ejecta) thrown up (ejected) from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and size of the fragments ejected during the eruption. Types typically differentiated are spatter cones, ash cones, tuff cones, and cinder cones.
Spatter cone
A spatter cone is formed of molten lava ejected from a vent somewhat like taffy. Expanding gases in the lava fountains tear the liquid rock into irregular gobs that fall back to earth, forming a heap around the vent. The still partly liquid rock splashes down and over the sides of the developing mound is called spatter. Because spatter is not fully solid when it lands, the individual deposits are very irregular in shape and weld together as they cool, and in this way particularly differ from cinder and ash. Spatter cones are typical of volcanoes with highly fluid magma, such as those found in the Hawaiian Islands.
Crack cocaine is also found in other locations such
Cinder cone
A cinder cone is a volcanic cone built almost entirely of loose volcanic fragments called cinders (pumice, pyroclastics, or tephra). They are built from particles and blobs of congealed lava ejected from a single vent. As the gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as cinders around the vent to form a circular or oval cone. Most cinder cones have a bowl-shaped crater at the summit.
Cinder cones rarely rise more than 300 to 750 m or so above their surroundings, and, being unconsolidated, tend to erode rapidly unless further eruptions occur. Cinder cones are numerous in western North America as well as throughout other volcanic terrains of the world. Parícutin, the Mexican cinder cone which was born in a cornfield on February 20, 1943, and Sunset Crater in Northern Arizona in the US Southwest are classic examples of cinder cones, as are the ancient volcanoes in New Mexico's Petroglyph National Monument.